math/big: remove stray whitespace in addMulVVW on amd64

Minor leftover from CL 74851.

Change-Id: I1b56afcde3c505ba77a0f79e8ae9b01000362298
GitHub-Last-Rev: 87e97571a58d5eadd63a28226543aaf1510a7b02
GitHub-Pull-Request: golang/go#48942
Reviewed-on: https://go-review.googlesource.com/c/go/+/355629
Reviewed-by: Robert Griesemer <gri@golang.org>
Trust: Daniel Martí <mvdan@mvdan.cc>
Trust: Alexander Rakoczy <alex@golang.org>
diff --git a/src/math/big/arith_amd64.s b/src/math/big/arith_amd64.s
index 59be952..5c72a27 100644
--- a/src/math/big/arith_amd64.s
+++ b/src/math/big/arith_amd64.s
@@ -379,7 +379,7 @@
 
 // func addMulVVW(z, x []Word, y Word) (c Word)
 TEXT ·addMulVVW(SB),NOSPLIT,$0
-	CMPB    ·support_adx(SB), $1
+	CMPB ·support_adx(SB), $1
 	JEQ adx
 	MOVQ z+0(FP), R10
 	MOVQ x+24(FP), R8